Re: The GPS Myth, Mythbusted ?

Quatro wrote:
On Jun 13, 10:51 pm, Tom Roberts <tjroberts...@xxxxxxxxxxxxx> wrote:
relativity accumulates, because gravity is monopole,
then motion also accumulate, must be also monopole

Hmmm. The time difference obtained in comparing identical clocks in a satellite and on the ground accumulates because they are located at different heights in a gravitational potential, and are moving at different speeds relative to a locally-inertial frame (here the ECI).

This has nothing to do with any multi-pole expansion of "gravity" (or of "motion" which AFAICT cannot possibly be expanded as multi-poles).


while i can see now, that magnetism is not a monopole,
so the satellites in motion does not accumulate,
the only other theory i know which accumulate is entropy
which must also be a monopole

You are rather confused about what a multi-pole expansion is, and how the various terms in such an expansion are related to physics.


a modern GPS receiver does not use its own
clock in determining its position, it uses 4 (or more) satellite
signals. In effect it is using the vastly more accurate satellite clocks
instead of its own, rather poor clock. Indeed, there is no need for a
clock in the receiver at all.

but Sir, the calculations requires local time in
order to do the position properly

No, a direct measurement of local time is not needed. With 4 or more satellites in view, a given event at the receiver is specified with 4 unknowns: latitude, longitude, altitude, and local time. These 4 unknowns can be determined by fitting to the signals received from 4 or more satellites. No local value of local time is needed (the receiver must be able to accurately measure time differences of a few seconds; an ordinary crystal oscillator is sufficiently accurate for this). The more satellites that contribute data to the fit, the more accurate the result is likely to be.


you cannot trust on a local time you get from
far away in the wilderness !!!

No. But GPS receivers do trust the fit I described above -- it DETERMINES the local time. To much better accuracy than any local clock could do (unless it is a set of atomic clocks).

Typical errors for a single fit as described above are
on the order of 10 ns, FAR better than any crystal or
mechanical oscillator can do. A GPS receiver at rest
on the surface and with the right software can to a
lot better (averaging over many hours)....


Tom Roberts
.

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